A conventional inter-roller conveyance control device is adapted to control the conveyance of an object to be conveyed between two rollers while applying tension thereto in order that the conveyed object does not become slack between the two rollers. Accordingly, the inter-roller conveyance control device often includes a tension control calculation unit that performs a calculation involved in feedback control including PI control, i.e., proportional integral control, or PID control, i.e., proportional integral and derivative control, such that the tension applied to the object to be conveyed corresponds to the tension being set. On the basis of the calculation performed in the feedback control, the tension control calculation unit corrects a speed command for a tension shaft being one of two shafts of the two rollers and adjusts a difference in speed between the shaft and a speed shaft being the other shaft to control the tension generated in the object to be conveyed between the rollers. In order for the inter-roller conveyance control device to stably convey the object to be conveyed, it is required to stably perform the tension control and properly set a gain of a tension controller. In a general inter-roller conveyance control device, a user observes a variation in the tension while performing inter-roller conveyance and changes a control gain through trial and error, which takes much time and effort to perform the adjustment as well as causes variations in stability depending on proficiency of the user.
Patent Literature 1 discloses an example of a technique that automatically adjusts the control gain of the tension control calculation unit by including a control gain change necessity determination unit in the inter-roller conveyance control device, setting the control gain high in an initial conveyance operation and, when the waveform of a detected tension value is oscillatory, gradually reducing the control gain by a determination of the change necessity determination unit to search for an appropriate control gain.